SONOCHEMICAL ACTIVATION OF HEMATOPORPHYRIN - AN ESR STUDY

The production of 2,2,6,6-tetramethyl-4-piperidone-N-oxyl by reaction of 2,2,6,6-tetramethyl-4-piperidone (TMPone) with ultrasonically gener ated active species in oxygenated solutions of hematoporphyrin (Hp) wa s studied by electron spin resonance: spectroscopy. The nitroxide prod uction rate in air-saturated TMPone solutions in phosphate-buffered sa line of pH 9.0 was significantly higher in the presence of Hp than in its absence. The enhancement of nitroxide production by Hp was signifi cantly inhibited in the presence of sodium azide or histidine in the s olution. The production rate with Hp was doubled by substitution of de uterium oxide, while the rate without Hp increased only modestly. Thes e results suggest that a substantial amount of active oxygen can be ge nerated by ultrasound in aqueous solutions of Hp. Since the production rate was not reduced by mannitol and no nitroxide was produced in nit rogen-saturated solutions, it appears that hydroxyl radicals do not ac count for a major portion of the active oxygen species which reacted w ith TMPone to yield a nitroxide.